Helicopter is a highly complex aircraft. It is said that a helicopter is two thousand parts flying together in one formation. This complexity contributes to the cost of production and operation and to the danger inherent in operating a helicopter. One of the factors contributing to the complexity of the helicopter design is the necessity to connect numerous control mechanisms, such as variable pitch angle control, collective control, etc., to the rotor blades via a rotating shaft. This complexity is further exacerbated by the flexible connection of the rotor blades to the shaft to allow for varying pitch angle and blade articulation necessary to compensate for lift deferential in the advancing and retreating phases of the cycle of rotation. The flexibility considerations dictated by the design of helicopter control mechanisms must be combined with structural strength dictated by the fact that the helicopter fuselage is supported in the air by the rotating rotor blades flexibly attached to the rotating shaft. These divergent factors greatly contribute to the complexity of design and operation and to the cost of production of helicopters. It would be desirable to provide a shaftless rotating wing aircraft or a rotating wing aircraft with a simplified or stationary main rotor shaft.
Helicopters are both dangerous and fragile. When on the ground, rotating rotor blades, which typically extend far beyond the fuselage of the aircraft, are akin to giant swinging swords creating a dangerous zone in the vicinity of the aircraft. Helicopters often operate at low altitudes and near trees, power lines, antennae, buildings, and other structures. Rescue helicopters often operate near mountain cliffs, even at high altitude. For well known reasons of basic physics, the main rotor of a helicopter is relatively large, typically extending beyond the helicopter's body in most horizontal directions. Therefore, objects in the immediate vicinity of an operating helicopter present danger to the helicopter: if the main rotor strikes an object, the rotor is likely to disintegrate, and the helicopter will probably crash. It would be preferable to provide a way to safeguard the rotor, at least in low-impact contacts with external objects.
Another problem with rotary wing aircraft is that rotor tips generate rather violent eddies of air. This turbulence increases power drag on the engine and the resulting parasitic losses, decreasing aircraft efficiency. The problem is aggravated at higher rotation speeds, as well as at higher cruising speeds, because the losses increase at higher air speeds of the rotor tips. It would be beneficial to provide a rotor with reduced tendency to generate eddies at its tips.
Yet another problem inherent in typical helicopter designs, and particularly in military helicopter designs, is that pilot ejection is impracticable: ejecting in the vertical direction obviously does not work because the pilot would be killed by the rotor. Helicopter pilots, however, are subject to manifold dangers on the battlefield, possibly even more so than pilots of fixed-wing military aircraft. It would be desirable to provide helicopters with pilot ejection capability.
Still another problem of helicopter design is related to the fact that linear velocity of a point on the rotor blade is proportional to the radius of rotation of the point, increasing towards the tip of the blade. Therefore, more lift is generated at the tips of the blades than near the rotor shaft. This causes the rotor blades to bend up at the tips during rotation, causing the disk of rotation to curve and assume a concave shape. This creates aerodynamic inefficiencies. It would be desirable to keep the blades horizontal and maintain a relatively flat disk of rotation to improve aerodynamic efficiency. It would also be desirable to have blades wider at the tips and narrower at locations closer to the center of rotation, to generate more lift.
Unlike airplanes, helicopters often operate at low airspeeds. Low airspeeds make possible, at least theoretically, deployment of a parachute in case of mechanical failure or another emergency that would otherwise result in a freefall of the aircraft. A parachute could thus safely lower a disabled helicopter to the ground—if only the parachute could be deployed. But much like the problem of ejecting a pilot from a disabled helicopter, the rotor is in the way of the parachute. It would be advantageous to enable parachute deployment in a helicopter.
Similar problems are pertinent to gyroplanes. As used by the Federal Aviation Administration (FAA), the term “gyroplane” refers to an aircraft that gets lift from a freely turning rotary wing (rotor blades), and which derives its thrust from an engine-driven propeller. Historically, this type of aircraft has also been known as the autogiro and the gyrocopter.
A need thus exists for rotary wing aircraft with a simplified design of the rotor shaft, or with shaftless design. Additional need exists for rotary wing aircraft that provide some protection to the rotor during impacts with external objects. A further need exists for rotary wing aircraft with reduced power losses due to eddies generated by rotor tips. Still another need exists to maintain rotor blades relatively straight during rotation and to avoid rotor curling up at the tips. A still further need exist to have rotor-blades wider at the tips than at the center of rotation. Another need exists for rotary wing aircraft with pilot ejection capability. Yet another need exists for helicopters that can deploy a parachute in an emergency.